Process of improving artificial threads



Patented Jan. 29, 1935 UNITED STATES PATENT OFFICE Leon Lilienfeld,Vienna, Austria No Drawing.

Application May 29, 1929, Serial No.

367 ,148. In Great Britain June 11, 1928 3 Claims.

This invention has for an object the treatment of artificial threads ofhigh dry tenacity, exceeding 2 grams, or even 3, 4, or 5 grams perdenier or even more, for imparting to such threads a de- 5 sirabledegree of extensibility.

In my Patents Nos. 1,683,199and 1,683,200, (the former being now issued,Reissue No. 18,170), I have described the manufacture from viscose ofartificial threads of high dry tenacity, exceeding 2 grams, or even 3, 4or 5 grams per denier or more, by a process comprising coagulation ofthe viscose formed into threads by means of strong mineral acid,particularly strong sulphuric acid of at least 50 to per cent. strength,preferably of at least to per cent. strength.

The present invention constitutes an improvement of the process andproduct described in said patent in that artificial threads producedaccording to the said patent acquire an increase in extensibility whentreated in accordance with the process of the present invention withoutexperiencing any considerable decrease in strength or lustre.

The present invention also constitutes an improvement on the inventiondescribed in my copending application Ser. No. 186,575 filed April 25,1927, in which has been set forth also several procedures for increasingthe extensibility of artificial threads of high dry tenacity, exceedingtwo grams per denier, produced'from viscose in accordance with thedisclosure of the above mentioned Patents Nos. 1,683,199 and 1,683,200,one of which procedures of increasing the extensibility consists intreating dry, moist or wet threads with caustic alkali solutions, assodium hydroxide or potassium hydroxide, of certain specifiedconcentrations under conditions which permit shrinkage of the thread tooccur. I

In the last mentioned co-pending application the use of aqueoussolutions of alkali hydroxide of not less than 15 per cent alkalihydroxide, preferably not less than 18 per cent of alkali hydroxide(calculated as NaOH) has been described as particularly suitable forproducing the shrinking eflect.

When proceeding in accordance with one illustrative example of theprocess as described in my said co-pending application Ser. No. 186,575viscose silk, made according to the process as described in my saidPatents Nos. 1,683,199 and 1,683,200 is, for example, introduced, inthe. finished, dried, but preferably unbleached state, in the form ofhanks, without stretching, into an aqueous caustic soda solution of18-25 per cent. strength at a temperature of 15-18 C. After a period of1-5 minutes, it is removed and then introduced, if desired, afterremoval of the excess caustic soda by centrifuging or pressing, and/or,if desired after a short washing, into sulphuric acid of 5-10 per cent.strength at room temperature for about 5 minutes, or into a hot or coldwater solution of ammonium sulphate of 5-25 per cent. strength or intohydrochloric acid of 4 per cent. strength. It is then washed, ifdesired, bleached and dried without stretching or under moderatetension.

My further researches into the action of alkali hydroxide solutions inproducing the results in question, and upon which the present disclosureis based, have disclosed the fact that certain solutions of alkalihydroxide containing less than 15 per cent. of alkali hydroxide(calculated at NaOH) give unexpectedly different results from othersolutions also containing less than 15 per cent. alkali hydroxide(calculated as NaOH) When operating upon artificial threads of thecharacter described in my said Patents Nos. 1,683,199 and 1,683,200 withsolutions of caustic soda of less than 15 per cent. strength accordingto the process described above for solutions of caustic soda of at least15 per cent. strength, unexpected results as shown in the followingenumeration appearz- (a) Caustic soda solution of 1 per cent. strengthgives practically no result.

(b) Caustic soda solution of 2 per cent. strength gives a very. slightincrease of the extensibility.

(c) Caustic soda solution of 3 per cent. strength gives a noticeableincrease of extensibility.

(d) Caustic soda solution of 4 per cent. strength gives a good increaseof extensibility.

(e) Caustic soda solution of 5 per cent. strength gives an excellentincrease of extensibility.

(f) Caustic soda solutions of 6, 7, 8, 10, 12, and 13 per cent. strengthgive a considerable increase of extensibility, but in some instancescause a tremendous decrease of the dry and wet tenacities and, inaddition to this, in many cases spoil the lustre of the artificial silkentirely.

It will be seen from the above that while solutions of caustic sodacontaining from 2 to 6 per cent. caustic soda give what may be regardedas useful increases in extensibility, those containing from 6 to 13 percent caustic soda, although favorably affecting the extensibility of thethread are practically less useful owing to the ill efiect which theyleave on other essential properties of the silk. The use of NaOHsolutions of 5 to 10% strength is claimed in a copending applicationSerial No. 750,017, filed Oct. 25, 1934.

Other alkali metal hydroxides such as potassium hydroxide may beemployed in practicing the present process and in this event it shouldbe used in the same molecular proportions as the sodium hydroxide. Theappended claims are intended as including the use of sodium hydroxide,potassium hydroxide or any equivalent.

The present invention is applicable not only to the treatment ofartificial threads as such (e. g. artificial silk), in the form of spunthreads, yarn in hanks or cops or in the form of warp or twisted yarn orthe like, but also to artificial threads (e. g. artificial silk orstaple fibre) in the form of woven fabrics. It is also applicable tothreads or fabrics consisting wholly of artificial fibre (e. g.artificial silk, artificial wool, or staple fibre) and to mixed threadsof fabrics, that is fibres or fabrics containing in addition to theartificial threads another fibrous material, for instance naturalcotton, silk, wool or the like. The expression artificial threadthroughout the application is intended to include, wherever the contextpermits, artificial threads such as artificial silk, artificial cotton,artificial wool, artificial hair and so on, in any of the formshereinbefore mentioned.

The success of the present process depends upon the fact that theartificial threads, or the materials consisting of or containing themare treated with the caustic alkali solution, by immersion or sprayingor in any other suitable manner, While substantially free from tensionor under conditions permitting shrinkage to occur. That is to say,either the material under treatment may not be subjected to tensionduring or after the treatment, or, if tension is applied it must besubsequently discontinued or reduced. The material or thread may beeither dry, moist or wet at the commencement of the treatment to beapplied.

I claim:

1. The process for increasing the extensibility of artificial thread ofhigh dry tenacity, exceeding 2 grams per denier, of the kind producedfrom viscose by coagulation thereof with a strong mineral acid, whichcomprises treating the said thread with an aqueous caustic alkalisolution containing alkali hydroxide between and including the limits of2 per cent and 5 per cent. (calculated as NaOH) under conditionspermitting shrinkage of the thread to occur.

2. The process for increasing the extensibility of artificial thread ofhigh dry tenacity, exceeding 2 grams per denier, of the type obtainableaccording to United States Patent Nos. 1,683,199 and 1,683,200 whichcomprises treating the said artificial thread with an aqueous causticalkali solution containing from about 2 to about 5 per cent. inclusiveof alkali hydroxide (calculated as NaOH) under conditions permittingshrinkage to occur 3. The process for increasing the extensibility ofartificial thread of the type obtainable by coagulating viscose with astrong mineral acid, including sulphuric acid, equivalent to at least 50per cent sulphuric acid which comprises contacting the said artificialthread with an aqueous solution containing from 2 to 5 per cent.inclusive of alkali hydroxide, calculated as NaOH, under conditionspermitting shrinkage of the thread to occur.

LEON LILIENFELD.

